The present invention relates to a valve having a backward flow prevention function disposed in a tank. Especially, the present invention relates a valve which changes a flow direction of a guided fluid at an outlet side while a decrease of supply ability of the fluid in accordance with the change of the flow direction is prevented. Also, the present invention relates to a valve made of plastic integrally welded with a tank, wherein a valve seat can be securely closed by a valve member.
In a port for supplying a fuel in a fuel tank of an automobile, a valve having backward flow prevention means is provided so that gasoline does not flow backwardly at the time of filling a fuel.
In case a fuel tank 120 provided with a valve 100 is made of plastics, as shown in FIG. 16, the valve 100 is made of plastics and has a cylindrical shape provided with an annular outer peripheral flange 103 in a middle portion thereof, and front and rear portions of the outer peripheral flange 103 are formed as an insertion cylinder portion 101 and an attachment cylinder portion 102 for a filler hose 130. Then, a distal end opening of the insertion cylinder portion 101 is oriented in a direction perpendicular to a center line of the insertion cylinder portion 101, and an open end surface of the opening is constituted as a valve seat, to which a plate-like valve member 105 is urged against the valve seat in a vertically downward direction. The insertion cylinder portion 101 is inserted in a horizontal direction into an attachment hole 121 formed in the fuel tank 120, and the outer peripheral flange 103 is disposed to abut against and welded to a portion of a surrounding wall 122 of the attachment hole 121 in the fuel tank 120.
In the valve 100 structured as describe above, the valve 100 is attached to the fuel tank 120 by inserting and welding the insertion cylinder portion 101 of the valve 100 into the attachment hole 121 in the fuel tank 120. Thus, there is an advantage that even if an internal pressure of the fuel tank 120 becomes high, a back flow of the fuel from the fuel tank 120 is prevented. On the contrary, there is a disadvantage that a direction of a flow of a fluid, such as gasoline, guided by the valve 100 from the filler hose 130 toward the fuel tank 120 is not changed at an outlet side of the valve 100, and the fluid flows into the fuel tank 120 as it is.
In view of the above, as shown in FIG. 17, there has been prepared a cylindrical valve 100 made of plastics and provided with an outer peripheral flange 103 in an annular shape at a middle portion thereof, and front and rear of the outer peripheral flange 103 are formed as an insertion cylinder portion 101 and an attachment cylinder portion 102. Further, an upper portion of the distal end opening portion of the insertion cylinder portion 101 is closed by a closing plate portion 104, and an open end surface of an opening in a semi-circular arch shape, which orients in a direction perpendicularly to a center line of the cylinder portion and is formed between a lower end rim of the closing plate portion 104 and the distal end opening portion, is formed as a valve seat. And, a plate-like valve member 105 is provided to be urged against the valve seat in a vertically downward direction. The valve 100 is structured such that in a condition that the insertion cylinder portion 101 is inserted into an attachment hole 121 formed in the fuel tank 120, the outer peripheral flange 103 abuts against and is welded to a surrounding wall 122 of the attachment hole 121 in the fuel tank 120.
However, in the valve 100 structured as described above, even though there is an advantage that a direction of a fluid, such as supply fuel, is changed at the distal end side of the valve 100 attached to the fuel tank 120 so that the fuel can be supplied to the fuel tank 120, there is a disadvantage that an area of the opening at the outlet side of the valve 100 is extremely smaller than an area of the opening at the inlet side of the valve 100, so that an ability of smoothly supplying fuel can not be obtained.
The present invention has been made to solve the above disadvantages in the conventional valve, and a main object of the present invention is to provide a valve in which a direction of the a supply fluid is changed at a distal end side of the valve while preventing a decrease of fluid supply characteristic in accordance with the change of the flow direction of the fluid.
Another object of the invention is to provide a valve as stated above, wherein a decrease of fluid cutoff characteristic induced by the means for preventing the decrease of fluid supplying characteristic can be effectively prevented.
Further objects and advantages of the invention will be apparent from the following description of the invention.